2018 Volume 84 Issue 4 Pages 275-281
We collected 1017 and 1931 isolates of wheat eyespot pathogen from 555 fields in various regions of Hokkaido in 1989 and 1992, respectively. Of these, 52.3% in 1989 and 43.7% in 1992 were identified as Oculimacula acuformis based on mycelial growth and culture morphology. The others (47.7% in 1989 and 56.7% in 1992) were O. yallundae. The 2-year data showed that O. acuformis was widely distributed in Hokkaido and was the dominant species in the northern and eastern regions. The susceptibility of O. yallundae and O. acuformis to demethylation inhibitor (DMI) fungicides was tested. The EC50 values for propiconazole ranged from 0.16 to 0.32 ppm and 1.0 to 4.5 ppm, and those for prochloraz ranged from 0.03 to 0.09 ppm and 0.04 to 0.18 ppm in O. yallundae and O. acuformis, respectively. The 2-year results indicate that the susceptibility of O. acuformis to propiconazole was relatively low. Efficacy of propiconazole and prochloraz on wheat eyespot was investigated in the fields where the proportion of O. acuformis was different from 5.0 to 100%. Propiconazole was effective in the fields dominated by O. yallundae, whereas the effect was not observed in those dominated by O. acuformis. Prochloraz had a stable effect in all the fields tested.